1. Field of the Invention
The present invention relates to a mechanical seal unit for pumps. More specifically, the present invention relates to a mechanical seal unit which can be suitably used for a pump which is strictly required to prevent inclusion of abrasion particles or dust into a fluid moving through the pump, such particles being inevitably produced from abrasion of sealing contact faces as they rotate slidably in a relatively opposite direction in a fluid tight condition.
The present invention further relates to a mechanical seal unit which otherwise may easily cause high friction heat, an abrasive mark and burn-in.
2. Description of the Related Art
A conventional mechanical seal for pumps may often cause pollution of liquids which are pumped through from abrasion particles or dust from wear of two sealing surfaces contacting slidably and sealably with each other. However, some types of pumps, for instance, those for extraordinary purified liquid pure water or extra-pure water for manufacturing and cleaning semi-conductors and LCDs must be strictly controlled to be free from inclusion of wear dust.
Biotechnology, medical laboratories and food-processing also require the same strict control of the liquid quality to be pumped. However, a suitable mechanical seal unit has not been proposed to solve this drawback.
For gas tight sealing, there is one known mechanical seal unit which is provided with a gas passage groove disposed on one of the two slidable seal faces for releasing wear particles out of the pump. This prior mechanical seal unit has a drawback in that the gas leaks through the passage groove which is communicative with the exterior or an atmosphere of a relatively low pressure even when the pump operation is stopped.
It is therefore an object of the present invention to provide mechanical seal unit which is constructed such that it enables an effective discharging of abrasion particles which are inevitably produced from the seal faces as they slidably move or rotate on each other.
The invented mechanical seal unit for pumps includes a fixed seal ring and a rotatable seal ring each providing a seal contact face such that the two seal faces slidably engage with each other in a fluid tight fashion. One of the fixed seal ring and the rotatable seal ring has on the contact face at least one inlet groove open exclusively to a higher pressure space, while the other of said two seal rings has on the contact seal face at least one outlet groove open exclusively to a lower pressure space or the exterior of the pump. The inlet groove and the outlet groove partially communicate with each other and jointly form an fluid passage only temporarily during relatively opposite rotation of the two contact faces.
In preferred embodiment of the present invention, the inlet groove may be disposed on the rotatable seal ring and said outlet groove may be disposed on the fixed seal ring, and said inlet and outlet groove have the same configuration.
For the configuration, the inlet groove may have a linear shape. Alternatively, the inlet groove may have a U-shape or V-shape.